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Recovery Strategy for the Hickorynut and the Kidneyshell [Final Version]

Habitat – Kidneyshell

 Habitat Identification: The Kidneyshell prefers shallow areas with clear, swift-flowing water and substrates of firmly-packed coarse gravel and sand.  In the Great Lakes it has been found on gravel shoals in Lake Erie and Lake St. Clair. 

 Currently Occupied Habitat:

Geospatial Description: Habitat in need of conservation for the Kidneyshell has been geospatially located using the methods developed by McGoldrick et al (2005) (Figures 9 & 10) who recommend using the Ontario Ministry of Natural Resource’s Aquatic Landscape Inventory Software (ALIS version 1) (Stanfield and Kuyvenhoven 2005) as the base unit for definition of important habitat within riverine systems.  The ALIS system employs a valley classification approach to define river segments with similar habitat and continuity on the basis of hydrography, surficial geology, slope, position, upstream drainage area, climate, landcover and the presence of instream barriers. For Great Lakes populations where ALIS segments can not be employed, McGoldrick et al (2005) recommend using a 5km buffer around known species occurrences. The 5km buffer was selected in light of the spatial extent of historic sampling within Lake St. Clair.  Within all identified river segments the width of the habitat zone is defined as the area from the mid-channel point to bankfull width on both the left and right banks.

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Figure 9: Currently occupied habitat zone of the Kidneyshell in the Sydenham and Ausable rivers. Areas within this zone matching the functional description should be considered habitat in need of conservation.

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Figure 10: Currently occupied habitat zone of the Kidneyshell in the Lake St Clair delta. Areas within this zone matching the functional description should be considered habitat in need of conservation.

Functional Description:

Within the area defined under currently occupied habitat areas meeting the characteristics described below are deemed to represent habitat in need of conservation:

  • permanently wetted and
  • of a stream order greater than 2 (riverine population only) and
  • having firmly-packed coarse gravel and sand substrates and
  • swift-flowing waters (riverine populations only) or
  • gravel shoals  (Great Lakes populations).

           Activities Likely to Impact Currently Occupied Habitat

The currently occupied habitat of the Kidneyshell could be negatively affected by a variety of activities.  Direct destruction could result from in-stream activities such as dredging, bridge and pipeline crossings or the construction of dams.  Habitat could also be negatively affected by any land-based activities that affect water quality or quantity.  Such activities would include, but are not limited to, the input of nutrients, sediment and toxic substances through improperly treated storm water, cultivation of riparian lands, unfettered access of livestock to the river, channelization and drainage works, water taking, aggregate extraction, and the release of improperly treated sewage. 

When dealing with freshwater mussels it is necessary to consider not only the physical and chemical components of habitat but also the biological. Any activity which disrupts the connectivity between Kidneyshell populations and their host species (see section on Reproduction) may result in the destruction of habitat. Activities which may disrupt the mussel-host relationship include, but are not limited to, damming, dewatering and sport or commercial harvest.  Note that activities occurring outside the currently occupied habitat zone may affect the host population within the zone (e.g., downstream damming activities may prevent the movement of fish into the zone during the period of mussel reproduction (September 1 – January 1)). Any activity that impacts a host population within an area of currently occupied habitat should be evaluated to ensure that the reproductive cycle is not disrupted.

Historically occupied habitat: Historically occupied habitat is defined as all areas where the Kidneyshell is known to have once occurred but is no longer found. Evidence for occurrence may be through records of historically collected live individuals or shells or through recent collects of weathered shells. Historically occupied habitat for the Kidneyshell includes a 50 km of the Lower Grand River from Caledonia to Port Maitland, a small portion of the Welland River, and a stretch of the Thames River between London and Chatham.  Historically occupied areas in the Detroit River, Lake Erie and Niagara River will only function as potential recovery habitat if the impacts of dreissenid mussels can be eliminated.

Critical Habitat: The identification of critical habitat requires a thorough knowledge of the species needs during all life stages as well as an understanding of the distribution, quantity, and quality of habitat across the range of the species. At present, this information is not available for the Kidneyshell although Table 3 outlines activities that would assist with obtaining the required information. The activities listed in Table 4 are not exhaustive but outline the range and scope of actions identified by the Recovery Team as necessary to identify critical habitat for the Kidneyshell. It is likely that the process of investigating the actions in Table 3 will lead to the discovery of further knowledge gaps that will have to be addressed. Until critical habitat can be defined the recovery team has identified the areas listed in the currently occupied habitat section as areas in need of conservation.

Table 3: Schedule of activities to identify critical habitat

ActivityApproximate Time Frame1
Conduct mussel population surveys2006-2008
Assess habitat conditions in occupied areas (e.g., flow, substrate, water clarity and quality)2006-2008
Determine any life stage differences in habitat use2007-2009
Survey and map areas of suitable but unused habitat within historical range2008-2010
Assess genetic structure of populations2006-2008
Determine host fish species2006
Conduct host fish population surveys2006-2008
Assess habitat use by host species2006-2008
Determine areas of overlap between mussel and host habitat2009-2010